The day after a strong earthquake leveled apartment buildings, damaged hospitals and flattened an elementary school, Mexicans mobilized Wednesday for a massive rescue effort, digging in a frantic search for survivors.

The death toll reached 230 people, with 100 in Mexico City and the rest distributed in surrounding states, Mexicans confronted scenes out of parents' worst nightmares as rescuers pulled children's bodies from the ruins of the primary school.

Thousands volunteered to provide medical care, food and water or to pick through buildings destroyed by Tuesday afternoon's quake, the second major temblor in the past month and the deadliest in three decades.

In the central Roma neighborhood, small stores stayed open around the clock, offering food to rescue workers and families of victims. A hardware store lent tools to people trying to claw through massive piles of debris.

In the capital, the 7.1-magnitude quake caused more than three dozen buildings to crumple and damaged hundreds more, a north-south band of destruction that scarred poor and wealthy neighborhoods alike.

At least 93 people died in the city, according to the coordinator of national civil defense, Luis Felipe Puente. That figure - and the overall death total of 223 as of late Wednesday afternoon - were revised downward slightly from earlier numbers released by the federal government.

"The priority continues to be rescuing people in collapsed structures and treating the wounded," President Enrique Pena Nieto wrote on Twitter on Wednesday, as he assessed damage in Mexico City and surrounding areas. Pena Nieto declared a three-day period of national mourning, the second time the government has made such a declaration this month.

The Mexican leader spoke to US President Donald Trump on Wednesday about the quake. Trump extended his condolences and offered assistance and search-and-rescue teams, which were quickly deployed, according to a statement from the White House.

Trump has had a testy relationship with the Mexican government and was criticized for not quickly contacting Pena Nieto after a deadly quake off the Pacific coast earlier this month.